{PING] [PATCH] Sign extension elimination

Mark Mitchell mark@codesourcery.com
Thu Apr 20 16:39:00 GMT 2006

I'm not finding this discussion very illuminating.

I'm trying to understand whether the current SEE pass is ready for
inclusion in the compiler.  Roger has approved it on technical merits,
but HJ has raised the issue that somehow this pass is a bad thing for

The fact that it doesn't presently help x86-64 doesn't worry me; the
only question is whether it works in some way that is going to actively
interfere with x86-64 support later.

So, may we please have a discussion about whether or not this pass is
inordinately PowerPC-specific?  I certainly didn't see anything in the
discussion of the pass that suggests that; it looked like the same
approach would probably work on other chips (ARM, MIPS) that have
similar instructions.  Is that correct?

What is it about the x86-64 instruction set that is so different from
PowerPC in this regard?  Are any of our other x86 experts concerned
about this pass?

Mark Mitchell
(650) 331-3385 x713

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